The Mosque occupies an important and effective aspect in the realm of the Islamic city. generally as to the effective role it plays in the Islamic city; moreover the important role played by the prayer and its functions as to the religious and social life of society; besides the administrative organizations; also by virtue of customs and traditions. The Mosque became a starting off for all that relying on the heavenly law; then rules and values of the society. The Mosque played its role starting off from the center of the city until the quarters dwelled by the population became independent; whereas each one taking a Mosque performing those functions. This what was represented by the cities to the north of Iraq and the subject matter which considered an exemplar for the cities on which those conditions applied to them with corresponding other neighboring cities which characterized by the specialty of analogy in the environmental and constructional factors, ,moreover the other impacts which relate to the planning nature of the city as to the rates and directions of the architectural extension inside the wall, topography of the location, and square available; besides the social factors which affected on limitation the form and design of the architectural elements. All that had the effect on appearing the form in which these mosques ended and forming the architectural personality. The research concentrated on the planning of the mosques in that area which took its origins from the first mosques which were represented by the prophet's mosque and clarifying its essence. But as to the architecture; the environment had its clear effect on moving into the closed design which prevailed since the fifth century A. H. nearly. Thus to find the guaranteeing handlings of this kind of building, using each element to adapt the environmental differences, constructional function, and kind of each material used in building.